1. Field of the Invention
The present invention relates to a communication apparatus to be connected to a telephone line.
2. Related Background Art
A prior art communication apparatus such as a facsimile device is configured as shown in FIG. 3.
In FIG. 3, numeral 1' denotes a communication apparatus, numeral 2 denotes a daughter telephone set, numeral 3 denotes a parallel telephone set, numeral 4 denotes a current detection circuit, numeral 5 denotes a communication unit for data modulation and demodulation, and numeral 16 denotes a control unit.
When the telephone set 2 connected to the communication apparatus 1' is off-hooked, a line current flows into the current detection circuit 4 and the control unit 16 detects that the telephone set 2 has captured the telephone line 9.
However, in the prior art apparatus, even if the telephone set 3 which is directly connected to the telephone line is off-hooked, no current flows into the current detection circuit 4 of the communication apparatus 1'. Accordingly, the control unit 16 cannot detect that the telephone line has been captured by the telephone set 3.
Accordingly, if a communication is to be made by the communication apparatus 1' or the telephone set 2 is off-hooked for speech when the telephone set is off-hooked, the telephone line is captured and it interferes the communication by the telephone set 3.
Further, once the telephone set 3 receives a call, the communication apparatus 1' cannot be started up.